I can tell you this by experiance now....  I have been seeing the 4G data dropping issue recently and I can say this "Do Not Keep Getting Replacement Devices" because it seems that when you activate the new device the issue takes longer to resolve.. 

I got a replacement device once and as soon as I notice that the replacement had the same issue I came to conclusion it wasnt the device, I basically called CS until they was able idnetified the issue, after I week of calling every few days I final got someone to resolve my dropping issue.

Normally I didnt have any issue with data until recently and this verified even more that the issue isnt the device....   Stop replacing that device because it isnt the problem.

Wish you luck on solutiion because it took me a week.